The embodiments herein generally relate to weapons systems, and, more particularly, to shoulder-launched multipurpose assault weapon (SMAW) systems and components.
As the name suggests, a SMAW system is a shoulder-launched rocket weapon system allowing for portability for its use. The SMAW launcher has a quick twist-lock interface allowing ammunition to be locked into the launcher with one quick push-and-twist motion. This unique interface presents a complex multidimensional measuring problem for the launcher assembly that includes a set of raised locking wedges inside the launcher, which prevent inadvertent and unintentional discharge of the weapon. The location of these locking wedges is critical to the reliability, function, and safety of these launchers.
Adding to this problem is the launch tube, which is a sub-part of the launcher's assembly, and has the same inspection problem, but with a slightly different dimension requirement, because at this point the launcher's aft ring has not been installed. Additionally, the current in-service launchers have two different versions of the locking wedge configuration. Moreover, the locking wedges have to be measured individually.
Because the location of the locking wedges is very critical to the reliability, function, and safety of the launchers, it has become commonplace to incorporate a phantom or imaginary inspection tool technique to maintain proper location of the locking wedges. This means there is an imaginary circle (e.g., approximately 10 mm in diameter) drawn at the front center of the locking wedge. The locations of the locking wedges are then measured from this 10 mm inspection tool to the aft-end of the launcher. This technique allows the center of the locking wedges to be held to a specific distance in from the aft-end of the launch tube (or launcher), regardless of the angle manufactured on the front edge of the locking wedges.
This inspection problem then splits into two different categories, and at each category the conventional techniques are different and present their own set of unique problems. First, at the sub-part level (described in further detail below with reference to the launch tube production); and second when building/rebuilding launchers (described in further detail below with reference to the building/rebuilding launchers).
Launch Tube Production:
This level of inspection has regularly been performed with a very expensive coordinate measuring machine (CMM) and a complicated inspection process. This presents some problems. First, the dimensions are internal and because of the length of the launch tube, a user needs a very large and expensive programmable CMM, which increases inspection costs. Second, this process relies on the CMM using a small and short angle as a starting point. Because it is difficult for these machines to pick up small and short angles, this stretches the accuracy limits of these machines, which results in a quality assurance problem. When the launch tubes are removed from molds, the internal and external dimensions are all achieved by the mold except the overall length. All internal parts of the launch tube such-as the locking wedges and the contact points are attached to the internal mandrel before the resin is injected into the mold.
When the tube is first removed from the mold, there is excess material on both the aft-end and the muzzle end of the launch tube. The unfinished launch tubes are then typically taken to a machine shop where they are put into a lathe to make a rough cut squaring up the aft-end. No dimensional tolerance is held at this point. All that is necessary is to square up the aft-end so an inspector has a square edge to work from for the following stages.
The tube is then sent to a gage lab where it is set up in a CMM to find the rough-cut length. A nominal dimension is subtracted from the rough-cut length found by the CMM, which provides the inspector with a known amount of material that has to be removed. The tube is then sent back to the machine shop with an exact amount of material that has to be removed. The material is removed from the aft-end, and the tube is turned around in the lathe and then the muzzle end is cut to the total overall length. At this point, it is assumed that the finished product is a good part. However, the problem is that there is a lot of room for human-error in this process and a lot of reason to question the recorded location of the locking wedges upon completion.
The quality of this product relies significantly on how well each process is performed, as well as how accurately the locking wedges are installed on the internal mold/mandrel before the resin is injected. Also, a CMM typically cannot accurately find the required angles, and the fact that molded parts are not perfectly round or flat, makes the entire procedure extremely subjective and error-prone. Finally, nowhere in this procedure is the position of the locking wedges actually measured. Thus, the conclusion reached is that the finished parts are sufficiently manufactured to use with the launchers. However, this cannot be verified with certainty.
Building/Rebuilding Launchers:
The SMAW special weapons technicians have been using various techniques over the years to measure this interface. According to a first method, one assumes the launch tube and aft-ring are manufactured and assembled correctly. According to a second method, a technique is implemented for using an old encasement with lines penciled on the outer surface identifying where the locking wedges are. Then, masking tape is applied to the outside of the launcher, and some lines are drawn on the outside of the launcher depicting where the locking wedges are on the inside. Next, the encasement is inserted with the pencil lines into the launcher. Thereafter, the encasement is rotated until it locks to see if the lines match up. According to a third method, a millijoule meter is installed to check if the alignment is correct.
Unfortunately, the conventional techniques require this interface to be within 0.2 mm (±0.0038 inch). Moreover, none of the above-mentioned procedures actually measure the locking wedge position individually, and accordingly all of these procedures are nothing more than an educated guess. Therefore, it is desirable to develop an improved SMAW assembly inspection tool and procedure that is readily adaptable in current weapon systems at reduced cost and complexity.